Consecutively calls to StringBuffer/StringBuilder .append should reuse the target object. This can improve the performance. Example: 
<pre>
String foo = " ";

StringBuffer buf = new StringBuffer();
buf.append("Hello"); // poor
buf.append(foo);
buf.append("World");

StringBuffer buf = new StringBuffer();
buf.append("Hello").append(foo).append("World"); // good
</pre>
